The present invention concerns an improved process--particularly convenient on an industrial level--for preparing alkansulphonamides.
There are known to be processes for preparing alkansulphonamides (general formula: RSO.sub.2 NR.sup.1 R.sup.2, wherein R is an alkyl group, or an alkyl group substituted by one or more chlorine atoms, and R.sup.1 and R.sup.2 are equal or different and can be hydrogen or an alkyl group) starting from alkansulphonylchlorides (general formula RSO.sub.2 X, wherein X is chlorine, bromine or iodine), which are caused to react with primary or secondary amines, or even with ammonia. With such processes, the treatment is carried out in suitable solvents. Among these solvents, the first ones to be adopted were the various ether compounds, preferably cyclic ethers. The most widely used of said ethers is tetrahydrofuran. Other tested solvents have shown considerable drawbacks. In particular, the nitroalkans evidenced that the solubility of the reaction products strongly depended on the temperature, hence requiring complicated and costly intermediate filtering steps. The use of toluene led to considerably lower reaction yields, while benzene involved all the problem connected to the use in industry of cancerous substances. The use of tetrahydrofuran--as a solvent for this reaction--is therefore still prevailing.
With all these processes it has however been necessary, up to now, to start from industrial raw materials having a high degree of purity, so as to keep this latter at the high levels required for the final product.
It has now been discovered that raw materials having a lower degree of purity may equally well be used, in the treatment of alkansulphonylchlorides for preparing alkansulphonamides, by suitably resorting to solvents other than those already used up to date.